Validity and reliability of a physical activity social support assessment scale.

Objective: To assess the validity and reliability of the Brazilian version of the physical activity social support scale for adults.
Methods: The scale was applied in conjunction with a face-to-face multi-dimensional questionnaire in 1,461 individuals aged between 18 and 79 years, living in Curitiba, Southeastern Brazil, between April and July 2009. The questionnaire was submitted to validity (factorial and construct) and reliability testing (internal consistency and reproducibility). Reliability was observed with the use of internal consistency, Cronbach's alpha, test-retest procedure with a one-week interval (n = 74) and intraclass correlation coefficient.
Results: Factorial analysis resulted in four factors with eigenvalues between 4.29 and 1.39, which explained 82.8% of the total variance. Factors 1 and 2 included questions about social support from friends for moderate to vigorous physical activities and walking, respectively. Factors 3 and 4 were comprised of groups of social support from the family for moderate to vigorous physical activities and walking, respectively. Reproducibility showed an intraclass correlation coefficient between 0.63 and 0.80 and alpha internal consistency between 0.87 and 0.91. Construct validity was observed from the significant association (p < 0.005) between scores of social support for walking and moderate to vigorous physical activities.
Conclusions: The instrument tested showed psychometric characteristics that were adequate for use in adult Brazilians.